JP2020007609A - Method for manufacturing tempered steel wire and apparatus for manufacturing the same - Google Patents

Abstract

To provide a method for refining steel wire with high efficiency and high quality and an apparatus therefor.SOLUTION: A fluidized bed 8 is used for heating at about 1000°C, quenching at room temperature, and reheating at about 500°C. In order to stabilize surface quality of a steel wire and furnace conditions, both or one of the following processes are performed: 1) a pickling tank 2 is provided before a heating furnace 3, and residual slag on a steel wire 1 is preliminarily pickled and removed, and 2) the fluidized sand of the heating furnace is discharged and washed with acid. High temperature heating of the fluidized bed is made possible, and efficiency of five times or more than that of an atmospheric furnace is realized. In terms of the heat transfer, the heat transfer efficiency is improved and the inefficiency of the heat transfer is reduced as wire diameter is reduced with convection as a main body. The cooling capacity of the fluidized bed at room temperature is more freely adjustable than the oil quenching, and resources can be saved by using the fluidized bed. The heat exhaust gas through a heat resistance blower is used for the fluidization and cascade heat utilization.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for efficiently producing a tempered steel wire and an apparatus for producing the steel wire.

Tempered steel wire is a high-strength steel wire made of carbon steel or low-alloy steel wire that has been subjected to initial heat treatment and wire drawing to form a wire of a predetermined diameter, and the metal structure has been tempered to martensite by quenching and tempering in the final process. And provided to springs, pins, needles, shafts, shafts, etc.
High quality materials, advanced processes, and advanced quality control are required for valve springs, bearing needles, and the like, which are high-grade products that require high strength and fatigue resistance. As a result of the top priority on quality, environmental measures such as energy saving and waste reduction in each process tend to be delayed.
The present invention aims to improve efficiency, save energy, and save resources (reduce waste) while securing higher quality in the final refining process for the above-mentioned high-grade products. Try to offer.

The quenching and tempering of the steel wire is processed while passing straight through three stages of heating, cooling and reheating.
The rate limiting of the production efficiency (t / h) is in the first heating step. With a large diameter wire having a diameter of about 10 mm, sufficient efficiency can be easily obtained by powerful induction heating or direct current heating, but with a thin wire having a diameter of 5 mm or less, the efficiency is remarkably reduced and the equipment cost of the method is reduced. The effect is a problem. For this reason, a multi-line combustion type heating furnace is usually used. In a heating furnace heated to about 1000 ° C., the atmosphere is usually controlled to prevent decarburization of the steel wire surface. The heating in the atmosphere has the following problems.

1) Combustion furnaces have a small heat transfer capacity (kcal / m2h) in principle compared to electric heating and lead bath / salt bath heating. Therefore, the required furnace length becomes longer, which is disadvantageous for space and heat loss.
2) In the wire drawing in the upstream process, the adhesion residue of the zinc phosphate film, which is a surface treatment for lubrication, is decomposed and reduced to generate molten Zn or Zn vapor, which forms extremely harmful defects on the steel wire surface. As a result, the surface treatment is prohibited by customers, and lime water treatment, shot peening treatment, and the like, which are extremely inefficient in terms of efficiency and cost, are substituted.
3) The cost of atmosphere control is unexpectedly high. There is a problem not only in the consumption of the inert gas but also in the durability of the heat-resistant steel.
4) Since the steel wire passes through the protection tube, the heat transfer is radiative without convection. Convection does not substantially occur even in a muffle furnace in which a large number of tubes are penetrated. The heat transfer coefficient is independent of the wire diameter, and the heating / cooling rate is simply inversely proportional to the wire diameter. As a result, the linear velocity V passing through the furnace is set in inverse proportion to the wire diameter D, and as a result, the production efficiency is proportional to the wire diameter, and decreases rapidly at a small diameter. Usually, the inconvenience is naturally not taken as a problem, but in the present invention, a problem also arises in that the efficiency is reduced when the small-diameter product is increased.

  In the past, lead baths and salt baths with high heat conductivity have been tried, but both have a trouble of working in a heating environment of about 1000 ° C., and have been abolished with pollution problems. The steel wire surface reacts with the strange slag to reduce the quality, the heat-resistant steel container reacts with the lead oxide on the liquid surface to cause corrosion and leakage, and the iron oxide is mixed in the salt bath and oxidized at the bottom of the bath Reactions caused pitting leaks and the like.

In recent years, fluidized bed furnaces have become widespread as rapid heating furnaces at a temperature of about 650 ° C. or lower. In this furnace, a burner is provided on the inner wall of the furnace, a sand layer of several hundred mm is deposited on the hearth, and is blown through the hearth to fluidize the layer and serve as a heat medium.
In the test at 900 ° C. or higher, iron oxide generated with the oxidation of steel reacts with fluidized sand and sinters to form a sand. Ca stearic acid (metal soap), which is frequently used as a wire drawing lubricant Decomposes in the furnace and organic components burn, but alkali and alkaline earth react with PO4 phosphate to cause sintering and adhesion. When Na borate is used, a glassy low melting point compound is used as a steel wire. There are many problems such as sticking to the surface and inducing quality deterioration, and it has not been put to practical use yet. From the above, a rapid heating method that can withstand 1000 ° C. is expected.

In the next stage of cooling to room temperature, a single wire can constitute a precision cooling device and water quenching is possible, which is advantageous for quality, cost and contamination. Oil quenching is usually applied because many books are complicated.
In oil quenching, a boiling phenomenon is involved. From high temperature to about 600 ° C, it is moderately cooled by film boiling, and at 600 to 400 ° C, nucleate boiling avoids pearlite transformation by considerable quenching. It is characterized by slow cooling, suppressing cracking during martensitic transformation, and easy to use.
On the other hand, even if there is no problem in quality, there are many problems in work environment and cost such as fire, odor, floor slip, and oil quality deterioration.

  Patent Document 1 discloses that an ordinary temperature fluidized bed is an alternative to oil quenching. The heat transfer coefficient of the fluidized bed is almost constant without temperature dependence and is at a level higher than that of oil. Therefore, if the intermittent contact is skillfully incorporated, a free cooling process can be performed. Although there is no embodiment, this is a cooling method that is desired to be utilized from the viewpoint of resource saving and safety.

In the third stage of reheating to about 500 ° C., recently, a fluidized bed furnace is frequently used in order to shorten the furnace length and to maintain uniformity. The value of the heat transfer coefficient is, for example, about 1000 (kcal / m2h ° C.), which is considerably large.
In actual operation, there is sufficient durability at 650 ° C. or lower unless strange foreign matter adheres to the steel wire and flows in from the upstream side.

The problem is that the amount of air used for fluidization is so large that it is on the same order of magnitude as the mass of the treated steel wire, and therefore the heating efficiency (= theoretical heat consumption / heat consumption) is extremely small (half the amount of a normal heating furnace). . There has been a plan for returning heat exhaust gas to flowing gas with a heat-resistant blower for a long time, but there is no price, performance, durability and convenience.
Patent Literature 2 discloses a method of circulating hot air by diverting an automotive turbocharger. This is an energy-saving measure that we want to make great use of.

In a multi-through heat treatment furnace, it is easy to operate only a single product type and a single wire diameter, but the product configuration usually includes a mixture of wire diameters and steel types. Efficiency is reduced when concentrated on a small diameter, and even if only a large diameter is used, the original capacity cannot be exceeded due to excessive load. This leads to a decrease in overall efficiency. It is desirable to perform parallel processing under different processing conditions in order to advance multi-product small lot production without difficulty.
Patent Literature 1 discloses a method in which the effective furnace length is adjustable for each pass and heating is performed at different temperatures at one furnace temperature. This is a means that we want to use to reduce overall costs.

Patent No. 6030801 Patent No. 5580466

In a method and an apparatus for producing a large number of high-quality fine-diameter refined steel wires through many kinds, small lots, and cost-effectively, in the first stage heating step, 1) heating without a suitable high-speed heating method and usually equipped with a burner A furnace is used and there is a problem with the furnace length and heating efficiency. 2) Atmosphere control is performed to prevent decarburization. At this time, the zinc phosphate coating treatment, which is the best lubrication treatment in the upstream drawing process, is harmful in this process and cannot be used. 3) There is a problem that the smaller the diameter, the lower the production efficiency is due to radiant heating.
In the next stage of cooling, oil quenching is good for quality but disadvantageous for work environment and cost. A room temperature fluidized bed has been proposed as an alternative, but there is no record.
In the third stage of reheating, a fluidized bed furnace having a high heating rate is used, but the blowing air reduces the heating efficiency to less than half. A measure to divert the heat exhaust gas to the blast has been proposed, but there is no record.

  An object of the present invention is to provide a method and an apparatus for producing a tempered steel wire which is more resource-saving and energy-saving than before and has a high production efficiency, and is effective for heating, cooling and reheating a fluidized bed. The problem to be solved is to make it applicable to

  In order to solve the above-mentioned problems, the heat transfer characteristics of fluidized bed furnaces, which had not been clarified before, were clarified from theory and experiments to improve the efficiency of heating and cooling, and observation and knowledge of work problems with high-temperature fluidized bed furnaces, which had not been successful until now, were found. Invented the following invention by taking measures.

  A first invention is a method for producing a tempered steel wire by running, heating, cooling, and reheating a steel wire, wherein when the steel wire is heated by a fluidized-bed furnace, 1) immediately before the fluidized-bed furnace, The steel wire is passed through an provided pickling tank to remove deposits on the surface of the steel wire. 2) Sand of a heating medium constituting the fluidized-bed furnace is appropriately discharged outside the furnace, washed with acid, and then returned to the furnace. And / or performing either one of the treatments.

  The second invention is an apparatus for producing a multi-pass heat treated steel wire comprising a heating furnace having a fluidized bed in which a heat medium is fluidized sand, a cooling tank, and a reheating furnace. A pickling tank for removing deposits on the surface of the steel wire is provided, and the heating furnace is provided with a heat source for heating the furnace to 850 ° C. or higher, a fluidizing blast source, and a steel wire shielding tube for adjusting the effective furnace length. A cleaning device for discharging sand, cleaning with acid, and returning to the furnace as necessary, is installed. The cooling tank is equipped with a cooling water pipe that keeps the temperature of the fluidized bed below 100 ° C, a room temperature fluidizing blast source, and heat transfer. A flow control valve for adjusting the air flow rate; a reheating furnace having an induction pipe having heat exhaust gas from the heating furnace as a main heat source, a burner or a resistance heating element as an auxiliary heat source, a fluidizing air supply source, and an effective furnace. With a steel wire shielding tube to adjust the length, heat exhaust gas is heated and reheated through a heat-resistant blower. It was fluidized blowing source is an apparatus for producing a microalloyed steel wire according to claim.

According to a third aspect of the present invention, the pickling solution for the steel wire is any one of hydrochloric acid, sulfuric acid and nitric acid, and the sand component of the heat medium is alumina (Al ₂ O ₃ ), zircon (ZrO.SiO ₂ ) or carbonized. An apparatus for producing a tempered steel wire according to the second invention, wherein the apparatus is any one of silicon (SiC).

  In a conventional fluidized bed furnace, when foreign matter adhering to the steel wire surface is brought into the fluidized bed at about 1000 ° C., the foreign matter reacts with the steel wire, heat medium sand, furnace body refractory, furnace body metal, etc. Although the steel wire quality deteriorates and causes various troubles and troubles in the furnace body, it is not used. However, in the present invention, the foreign matter is removed by pickling the steel wire immediately before heating or by pickling the sand in the furnace, and the fluidized bed is removed. A heating furnace can be applied to the high temperature.

The heat transfer characteristics of the fluidized bed were clarified from theory and actual measurements, and it was found that the value of the heat transfer coefficient α was inversely proportional to the 0.4th power of the wire diameter D, and applied to the present invention.
1) In a normal combustion type heating furnace, most of the heat transfer is radiation, in which case the heat transfer coefficient α is not affected by the wire diameter. The production efficiency is proportional to the wire diameter D, and the smaller the diameter, the lower the efficiency in proportion. In a fluidized bed, convection is mainly involved, and the α value increases rapidly at a small diameter under the influence of the wire diameter D. The decrease in efficiency is reduced in proportion to the 0.6th power of the wire diameter. It is more effective for heating small diameter products.

2) The heating rate is about 5 times or more that of the atmosphere furnace, and decarburization does not occur due to shortening of the heating time. The formation of a small amount of oxide film is not always inconvenient because it contributes to stabilization of friction during processing such as spring winding. No atmosphere control is required.
3) The required furnace length is shortened and energy efficiency is improved.
4) Since the refrigerant in the cooling tank is changed from oil to sand, it contributes to improvement of working environment and resource saving. Quality control is stable without deterioration of the refrigerant. Because of the fluidized bed, the cooling capacity can be adjusted up and down more freely than the quenching oil.

  The heat exhaust gas from the heating furnace is used in a reheating furnace in a cascade manner, and a part of the heat exhaust gas is suctioned and pressurized by a heat-resistant blower to be used as a fluidized air supply source for the heating furnace and reheating furnace, so the heating efficiency is significantly improved. And contribute to energy saving. Overall, cost reduction is achieved.

The schematic structure of the manufacturing apparatus of the tempered steel wire of the present invention is shown. The method for diversifying the processing conditions of heating, cooling and reheating in the present invention will be described. FIG. 3 is a diagram showing the relationship between the heat transfer coefficient and the wire diameter of the fluidized bed used in the present invention. 1 shows a heating wire of a steel wire in the present invention.

Hereinafter, an apparatus for implementing the method for producing a tempered steel wire of the present invention will be described with reference to FIG. The apparatus mainly comprises a pickling tank 2, a heating furnace 3 at about 1000 ° C. each having a fluidized bed, a cooling tank 4 at room temperature, and a reheating furnace 5 at about 500 ° C. After passing in parallel in the above order to clean the surface of the steel wire, quenching and tempering are performed.
The fluidized bed is an apparent liquid heat medium in which sand having a diameter of about 100 μm is deposited about 300 mm on a ventilation plate of a hearth, air is blown through the ventilation plate, and the deposited layer is expanded and fluidized. A fluidized-bed furnace in which is incorporated is used as a heating furnace having a high heat conductivity equivalent to that of a lead bath or a salt bath, for heating at about 650 ° C. or less, for cooling (patenting) at about 500 ° C., and the like.

  The former pickling tank has the following functions. As described above, the adhesion residue of the steel wire includes zinc phosphate, Ca stearate, and sodium borate. Oxides such as PO4, ZnO, NaO.B2O3, and CaO are generated by heating and thermal decomposition. The former three are easily reduced by the atmosphere and deteriorate the product surface. In a fluidized bed furnace, the atmosphere is oxidizing because there is a flame right above. Since the linear velocity is high, the oxide film thickness is small, but a part of the oxide film falls into the furnace and FeO is newly added. The acidic and reducing oxides, including fluidized sand, react variously due to the high temperature of about 1000 ° C, causing the coagulation phenomenon due to the lowering of the melting point, causing the sand to solidify, adhering to a part of the furnace body and the surface of the steel wire, and causing various reactions. It can be a source of trouble. This is why high temperature fluidized beds have not been put into practical use. The compound can be easily dissolved and separated in advance with an acid. If done well, the adhesion residue is removed by a process of several seconds to ten and several seconds.

  The heating furnace 3 in the first stage is provided with a ventilation chamber 6 at the bottom, a refractory ventilation plate 7 on the ceiling of the ventilation chamber 6, a fluidized bed 8 on the ventilation plate 7, a burner 9 and a flue 10 on the ceiling of the furnace. Further, a discharge hole 11 for liquid sand is provided near the outlet of the furnace, and a charging hole 12 for washed liquid sand is provided near the entrance. The discharged sand is subjected to a cleaning device 13 including a filter, a pickling tank, and a dehydrator to separate, dissolve and remove foreign matter mixed in the sand, and return to a charging hole. Ejection and regression may be continuous or intermittent. The feature of the fluidized-bed heating furnace is that the heat transfer coefficient between the steel wire and the steel wire is extremely large, so that high-speed heating is achieved.

The cooling tank 4 in the next stage is provided with a blower chamber 14, a fluidized bed 15, a water cooling pipe 16 for maintaining the fluidized bed 15 at about 100 ° C. or less, and a room temperature blower 18 having a pressure regulating valve 17 in a steel plate tank. . The upper part of the tank is open so that the wire temperature and other information can be easily checked.
Characteristics of fluidized-bed cooling are that it has a cooling capacity equal to or higher than that of quenching oil, and that the cooling capacity is stable without strange temperature dependence. Therefore, any cooling process can be easily set by appropriately suppressing the cooling capacity.

  The third-stage reheating furnace 5 has substantially the same structure as the heating furnace 3, but does not include a sand collecting / washing / returning device. On the ceiling, the flue 10 from the heating furnace 3 and the auxiliary burner 19 or the auxiliary resistance heating element 20 are provided in the fluidized bed. On the furnace side, a heat-resistant blower 0 that branches from a flue 10 of the heating furnace 3 and sucks and pressurizes hot exhaust gas to supply hot air to the blowing chambers of the heating furnace 3 and the reheating furnace 5 is provided. The hot air blowing avoids the conventional cooling of the furnace, and approximately doubles the heating efficiency.

FIG. 2 is a diagram for explaining a method of individually adjusting the heating temperature and the cooling rate of the steel wires when the plurality of steel wires travel.
When steel wires with different heating temperatures are processed in parallel, the furnace temperature is adjusted to the type of the highest temperature, and the lower steel wire shortens the effective furnace length to shorten the heating time. The ultimate heating temperature decreases. Specifically, the steel wire 1 passing through the heating furnace 3 is passed through the heat-resistant protective tube 21, and the length of penetration of the protective tube 21 into the furnace is appropriately set. In the steel wire 1, only radiant heating from the tube wall equal to the furnace temperature occurs in the tube, resulting in slow heating. Pipes are taken in and out from the upstream side.

When the cooling conditions are different, various methods can be used. 1) The intermittent shielding tube 22 is appropriately attached and detached from above from around the steel wire 1 to induce predetermined cooling. 2) Partition walls are provided in the front and rear and left and right sides of the blower chamber and the flow chamber, and the amount of blown air is individually set.
When the reheating temperature is different, the furnace temperature is set to the temperature of the type having the highest heating temperature as in the heating furnace, and the heat-resistant protective tube 23 is set to an appropriate length for the steel wire having a lower heating temperature from the downstream side. Installing.

Even if there is no pickling of the steel wire, it is an effective measure if the sand is properly washed and foreign substances are constantly removed. It is desirable to do both. Debris removal is an essential condition when using fluidized beds at high temperatures.
As the acid used for pickling steel wire and cleaning fluidized sand, one of hydrochloric acid, sulfuric acid and nitric acid is appropriate. As the sand as the heat medium, a substance that is difficult to react at a furnace temperature of about 1000 ° C. is selected. In addition to general zircon (ZrO.SiO2), alumina (Al2O3), silicon carbide (SiC) or the like is used alone. Similar precautions are required for furnace body refractories.

The heat transfer coefficient between the steel wire and the fluidized bed varies depending on the amount of blowing air (superficial velocity m3 / min / m2). As the air flow increases, it increases proportionally, becomes flat at a certain level, and is usually used at that level. However, in the case of cooling, the air flow may be reduced to an appropriate cooling rate.
The appropriate superficial superficial velocity in the case of heating and in the case of cooling are almost the same, but the blowing amount is different because the thermal expansion of gas is involved.

Analyze the heat conductivity of the fluidized bed. Although the heat transfer properties of a fluidized bed (described as "fluidized bed" in the literature) are cited and described in detail in many of the following documents, they are difficult to understand. Practical formulas were derived from the basic formulas of fluid mechanics and heat transfer engineering, and the method of solidifying from the measured values was adopted.
Literature: Masahiko Yoshida, Practical Thermal Engineering, P.1108-P.1113, Kurita Publishing Company

The heat transfer coefficient α is derived from the Nusselt number Nu, which is a dimensionless heat transfer coefficient.
Nu = α · D / λ, α = Nu · λ / D (1)
The Nusselt number Nu is related to the dimensionless Reynolds number Re indicating the flow state and the Prandtl number Pr indicating the physical properties of the fluid.
Nu = C ・ Rem ・ Prn (Pro / Prw) p −−−−− (2)
Re = V · D / (μ / ρ) −−−−− (3)
Pr = c · μ / λ −−−−− (4)
The following equation is derived from equations (1) and (2).
α = kD (m-1) ----- (5)
From the equation (5) and the following constant, the heat transfer coefficient α is inversely proportional to the wire diameter D raised to the 0.4th power. That is, in convection heat transfer, unlike radiation, the heat transfer coefficient increases rapidly as the wire diameter decreases.
The constants C, m, n, and p have the following values depending on the Re number.
Re number C mnp
1 to 40 0.75 0.4 0.37 0.25
40 ~ 1000 0.51 0.5 0.37 0.25
1000 ~ 200000 0.26 0.6 0.37 0.25
D; wire diameter λ; thermal conductivity c; specific heat μ; viscosity ρ; density Pro; number of mainstream Pr
Prw; number of wall Pr k; proportional constant

In the calculation, the physical properties of the fluidized bed, that is, specific heat, thermal conductivity, and viscosity, are unknown, but the approximate values of the former can be obtained from the expansion coefficient of the sand layer, and the viscosity is considered to be the same level as air.
FIG. 3 shows the relationship between the heat transfer coefficient α and the wire diameter D obtained by the above equation. Although the fragmentary actual measurement values drawn in the figure slightly deviate from the calculation formula, it is clear that the smaller the wire diameter, the larger α becomes. The radiation value αr from the hot sand is added to the convection component α to the actual value of the heat transfer coefficient αt. The average value of the radiation is about 150 (kcal / m2h ° C). The calculated value approximates the measured value, and the analysis by this method can be regarded as practical.
αt = α + αr ------ (6)
αr ≒ 150
Incidentally, the radiation αr is the same as the heat transfer coefficient of the atmosphere heating furnace. It can be seen that in the fluidized bed the heat transfer coefficient increases 4 to 9 times.

An increase in the heat transfer rate means an increase in the heating rate and a reduction in the heating time. If the value of the heat transfer coefficient α is known, the heating / cooling rate of the steel wire can be obtained by the following equation. FIG. 4 shows the heating diagram obtained by the calculation.
dθ / dt = 4α (θ−θo) / cpD (7)
When the wire diameter is 5 mm or less, the required heating time is several tens seconds or less. In such a short time, there is not enough time for decarburization to occur even if some oxidation occurs. As in the case of induction heating, atmosphere control becomes unnecessary. Similarly, the furnace length is greatly reduced, and the length of the furnace is shortened even if a new pickling tank is included.
The cooling curve is upside down in FIG. 4, and both are exponential asymptote from the initial temperature to the ambient temperature (furnace temperature or refrigerant temperature).

How the heat transfer coefficient α affects the production efficiency of the steel wire will be described.
The production efficiency P is represented by the following equation.
P = πρD2V / 4 −−−−− (8)
The linear velocity V is obtained by dividing the furnace length L by the passage time t (= heating time).
V = L / t (9)
The heating time is obtained by dividing the heating temperature Θ by the average heating rate θ ′.
t = Θ / θ ′ −−−− (10)
The average heating rate θ ′ is half of the maximum heating rate.
θ ′ = 4αΘ / cρD / 2 (11)
The following is derived from the above relational expression.
P = πLDα / 2c −−−− (12)
That is, the production efficiency is usually proportional to the product of the wire diameter D and the heat transfer coefficient α.
On the other hand, in the fluidized bed, the heat transfer coefficient α is affected by the wire diameter D as described above, and is given by the following equation.
P = πLD0.6α / 2c (13)
From the above, the production efficiency of the thin wire decreases in proportion to the wire diameter with respect to the maximum diameter in the case of radiant heating, whereas it decreases in proportion to the 0.6th power of the wire diameter in the case of convection heating. The degree of decrease is small. That is, the efficiency reduction due to the small diameter is reduced to some extent.

A feature of the present invention is that the fluidized bed is applicable to a high temperature furnace. Pickling of both or one of the steel wire and fluidized sand is an essential condition, but the practice of this part is omitted because it is easy for those skilled in the art, and the specifications of the new high-temperature fluidized bed are compared with those of the conventional heating furnace. The results are summarized in Table 1.
As prerequisites, 1) the reference wire diameter (= maximum diameter) was 5 mm, the design facility capacity was 100 kg / h / piece, and 2) the furnace temperature was 5% higher than the target heating temperature. In the atmosphere furnace of the comparative example, when the wire diameter is 2 mm, the efficiency is reduced to 40% of that of the reference diameter, but in the present invention, the efficiency is reduced to 60%.

  The method and apparatus for manufacturing a tempered steel wire according to the present invention can be easily replaced by an existing heat treatment plant, and contribute to improving productivity.

1: steel wire 2: pickling tank 3: heating furnace 4: cooling tank 5: reheating furnace 6: ventilation chamber 7; ventilation plate 8; fluidized bed 9; burner 10; flue 11; discharge hole 12; 13; cleaning device 14; blower chamber 15; fluidized bed 16; water cooling pipe 17; regulating valve 18; room temperature blower 19; auxiliary burner 20; resistance heating element 21; heat-resistant protective tube 22; intermittent shielding tube 23; heat-resistant protective tube 0; Heat resistant blower

Claims (3)

  In a method of manufacturing a tempered steel wire by running, heating, cooling and reheating a steel wire, when heating with a fluidized-bed furnace, 1) the steel wire is placed in a pickling tank provided immediately before the fluidized-bed furnace. 2) The sand of the heating medium constituting the fluidized bed furnace is discharged to the outside of the furnace as appropriate, washed with an acid, and then returned to the furnace. A method for producing a tempered steel wire, wherein one of the treatments is performed.   This is a parallel multi-pass heat-treated steel wire production system consisting of a heating furnace with a fluidized bed using fluidized sand as the heating medium, a cooling tank, and a reheating furnace. Is provided, and the heating furnace is provided with a heat source for heating the furnace to 850 ° C. or higher, a fluidizing blast source, and a steel wire shielding tube for adjusting the effective furnace length. Equipped with a washing device that discharges and cleans with acid and returns to the furnace, the cooling tank has a cooling water pipe that keeps the temperature of the fluidized bed below 100 ° C, a room temperature fluidizing blast source and fluidization that regulates the heat transfer coefficient. A recirculation furnace having an air flow control valve, an induction pipe having a heat exhaust gas from the heating furnace as a main heat source, a burner or a resistance heating element as an auxiliary heat source, a fluidizing air supply source, and a steel wire for adjusting an effective furnace length. A shield tube is provided, and the heat exhaust gas is used as a fluidized air supply source for the heating furnace / reheating furnace through a heat-resistant blower. Apparatus for producing a heat-treated steel wire, characterized in that. The pickling solution for the steel wire is any one of hydrochloric acid, sulfuric acid, or nitric acid, and the sand component of the heating medium is alumina (Al ₂ O ₃ ), zircon (ZrO.SiO ₂ ), or silicon carbide (SiC). The apparatus for producing a tempered steel wire according to claim 2, wherein the apparatus is a single type.

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